keppet-mcp

A Model Context Protocol server for Keppet Open Data — free, daily, USD-anchored data for the world's currencies, precious metals, crypto, reference rates and sovereign yield curves.

Zero dependencies. No API key. It is a thin typed wrapper over the public CDN (forge-arcana/kod-data via jsDelivr): every tool is a static GET, and convert does the USD-anchor math so your agent gets a number instead of a URL and a formula.

Run

npx keppet-mcp

or clone and run directly (Node ≥ 18):

node mcp/server.mjs

The server speaks newline-delimited JSON-RPC 2.0 over stdio — point any MCP client at it.

Configure an MCP client

Claude Desktop / Claude Code (claude_desktop_config.json or .mcp.json):

{
  "mcpServers": {
    "keppet": {
      "command": "npx",
      "args": ["-y", "keppet-mcp"]
    }
  }
}

Optional env var KOD_CDN overrides the base URL (e.g. to pin a commit SHA for reproducible results instead of @main).

Tools

| Tool | Arguments | Returns | |---|---|---| | list_datasets | — | Every dataset: unit, count, latest date, sources (discovery entry point). | | convert | from, to, amount? | Cross-rate + converted amount between any two instruments, across domains. | | get_fx | symbols? | FX rates, per USD. | | get_metals | symbols? | Metal spot prices, USD per troy ounce (XAU/XAG/XPT/XPD). | | get_crypto | symbols? | Crypto prices, USD. | | get_rates | — | Reference + policy interest rates, percent p.a. | | get_yield_curve | country? | Sovereign yield curve (tenor → yield); defaults to US. |

How convert works

Every value is anchored to USD, so any cross-rate is one division:

value_of_X_in_Y = usd_value(X) / usd_value(Y)

usd_value is how many USD one unit is worth: for fiat it's 1 / rate (rates are quoted per USD), for price domains (metals, crypto) it's the price itself, and USD is 1. The server resolves an instrument across fx → metals → crypto automatically, so convert("BTC","JPY") or convert("XAU","EUR") just work.

Notes

• Responses are cached in-process for 5 minutes — a burst of agent calls collapses to one network hit without serving stale data (the feeds update at most a few times a day).
• Tool failures come back as isError content (e.g. an unknown symbol), so the agent can recover rather than seeing a transport error.
• Data licensing and source attribution follow the upstream feeds; see the main project README.